Simple implementation of gpuimage chain texture

The chain shader The implementation of the

Realize chain shader The core idea of : Buffer objects with frames , The texture unit generated by the frame buffer object is the next shader Texture input ;
Source code

The core of frame buffer

/**  Set the frame buffer object  */
-(void)setuptextureSize:(CGSize)size{
    
    glGenFramebuffers(1, &_frameBufferID);
    glActiveTexture(GL_TEXTURE1);
    glGenTextures(1, &_textureID);
    glBindTexture(GL_TEXTURE_2D, _textureID);
    
    // -  there  size  It is filled with rendering view  Of size, Not the picture  size
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size.width, size.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glBindFramebuffer(GL_FRAMEBUFFER, _frameBufferID);
    
    // -  Framebuffer object 
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D, _textureID, 0);
    
    /*  Untie the texture , Unbind to rebind a new texture unit ;  If there is no unbinding operation ,  Then the output texture unit of the frame buffer is GL_TEXTURE1,  But if it is the output of one frame buffer and the input of another frame buffer ,  It will appear that the input and output are the same texture unit ;( As below shaderCompiler2, frameBuffer1 The output texture unit of is used as shaderCompiler2 The input unit of is  GL_TEXTURE1,  the shaderCompiler2 After frameBuffer2 The output texture unit of is also GL_TEXTURE1,  This is not possible ) glActiveTexture() :  Set the output texture unit of the frame buffer ; glUniform1i() :  Set up  shader  The input of texture ;  Input and output cannot be the same texture unit ; */
    glBindTexture(GL_TEXTURE_2D, 0);
}

- (GLuint)textureID{
    
    return _textureID;
}

- (GLuint)framebufferID{
    
    return _frameBufferID;
}

/**  Activate frame buffer  */
-(void)activityFrameBuffer{
    
    glBindFramebuffer(GL_FRAMEBUFFER, _frameBufferID);
}

Implementation of chain texture

// -  Input texture 
-(void)setupInputTexture{
    
    GLuint texture;
    UIImage *image = [UIImage imageNamed:@"gyy.jpg"];
    size_t width = CGImageGetWidth(image.CGImage);
    size_t height = CGImageGetHeight(image.CGImage);
    _bufferSize = CGSizeMake(width, height);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    void *imageData = malloc( height * width * 4 );
    
    CGContextRef context = CGBitmapContextCreate(imageData,
                                                 width,
                                                 height,
                                                 8,
                                                 4 * width,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    
    CGColorSpaceRelease( colorSpace );
    CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
    CGContextTranslateCTM(context, 0, height);
    CGContextScaleCTM (context, 1.0,-1.0);
    CGContextDrawImage( context, CGRectMake( 0, 0, width, height ), image.CGImage );
    CGContextRelease(context);
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D,
                 0,
                 GL_RGBA,
                 (GLint)width,
                 (GLint)height,
                 0,
                 GL_RGBA,
                 GL_UNSIGNED_BYTE,
                 imageData);
    free(imageData);
}

// -  Three shader programs  ( Original texture ->shaderCompiler1->frameBuffe1, frameBuffe1->shaderCompiler2->frameBuffe2, frameBuffe2->shaderCompiler3-> Render on screen )
-(void)setupShader{
    
    self.shaderCompiler1 = [[QGShaderCompiler alloc]initWithvshaderFileName:@"VertextShader2" fshaderFileName:@"FragmentShader2_06"];
    _position1 = [self.shaderCompiler1 addAttribute:@"position"];
    _texture1 = [self.shaderCompiler1 addAttribute:@"textCoordinate"];
    _uni1 = [self.shaderCompiler1 addUniform:@"colorMap"];

    
    self.shaderCompiler2 = [[QGShaderCompiler alloc]initWithvshaderFileName:@"VertextShader2" fshaderFileName:@"FragmentShader2_04"];
    _position2 = [self.shaderCompiler2 addAttribute:@"position"];
    _texture2 = [self.shaderCompiler2 addAttribute:@"textCoordinate"];
    _uni2 = [self.shaderCompiler2 addUniform:@"colorMap"];


    self.shaderCompiler3 = [[QGShaderCompiler alloc]initWithvshaderFileName:@"VertextShader2" fshaderFileName:@"FragmentShader2_14"];
    _position3 = [self.shaderCompiler3 addAttribute:@"position"];
    _texture3 = [self.shaderCompiler3 addAttribute:@"textCoordinate"];
    _uni3 = [self.shaderCompiler3 addUniform:@"colorMap"];
}

// -  Two frame buffer objects that provide output 
-(void)setupFrameBufferObj{
    
    self.frameBuffer1 = [[QGFrameBuffer alloc]initWithSize:self.frame.size];
    self.frameBuffer2 = [[QGFrameBuffer alloc]initWithSize:self.frame.size];
}

// -  Original texture ->shaderCompiler1->frameBuffe1
-(void)render1{
    
    [self.shaderCompiler1 glUseProgram];
    [self.frameBuffer1 activityFrameBuffer];
    glClearColor(1, 0, 0, 1);
    glClear(GL_COLOR_BUFFER_BIT);
    glViewport(0, 0, self.frame.size.width, self.frame.size.height);

    /*  The output texture unit of the known source texture is  GL_TEXTURE0;  The lower one  glUniform1i(_uni1, 0)  Yes, it will  GL_TEXTURE0  As  self.shaderCompiler1  Input texture of , QGFrameBuffer  Medium  glActiveTexture(GL_TEXTURE1);  Yes, it will  GL_TEXTURE1,  As a frame buffer texture output unit ; */
    glUniform1i(_uni1, 0);
    
    GLfloat vertices[] = {
    
        1.0, 1.0, 0.0,
        1.0, -1.0, 0.0,
        -1.0, 1.0, 0.0,
        
        1.0, -1.0, 0.0,
        -1.0, -1.0, 0.0,
        -1.0, 1.0, 0.0};
    
    GLfloat texturecoords[] ={
    
        1.0, 1.0,
        1.0, 0.0,
        0.0, 1.0,
        1.0, 0.0,
        0.0, 0.0,
        0.0, 1.0};
    
    glVertexAttribPointer(_position1, 3, GL_FLOAT, GL_FALSE,  sizeof(GLfloat) * 3, vertices);
    glVertexAttribPointer(_texture1, 2, GL_FLOAT, GL_FALSE,  sizeof(GLfloat) * 2, texturecoords);
    glDrawArrays(GL_TRIANGLES, 0, 6);
}

// - frameBuffe1->shaderCompiler2->frameBuffe2
-(void)render2{
    
    [self.shaderCompiler2 glUseProgram];
    [self.frameBuffer2 activityFrameBuffer];

    glClearColor(0, 1, 0, 1);
    glClear(GL_COLOR_BUFFER_BIT);
    glViewport(0, 0, self.frame.size.width, self.frame.size.height);
    
    /*  The front is known self.frameBuffer1 The output texture unit of is  GL_TEXTURE1; glActiveTexture(GL_TEXTURE2);  and  glBindTexture(GL_TEXTURE_2D, [self.frameBuffer1 textureID]);  Yes, it will  self.frameBuffer1 The output texture unit of is from  GL_TEXTURE1  Change it to  GL_TEXTURE2; glUniform1i(_uni2, 2)  Yes, it will  GL_TEXTURE2  As  self.shaderCompiler2  Input texture of ; QGFrameBuffer  Medium  glActiveTexture(GL_TEXTURE1);  Yes, it will  GL_TEXTURE1,  As a frame buffer texture output unit ; */
    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, [self.frameBuffer1 textureID]);
    glUniform1i(_uni2, 2);
    
    GLfloat vertices[] = {
    
        1.0, 1.0, 0.0,
        1.0, -1.0, 0.0,
        -1.0, 1.0, 0.0,
        
        1.0, -1.0, 0.0,
        -1.0, -1.0, 0.0,
        -1.0, 1.0, 0.0};
    
    GLfloat texturecoords[] ={
    
        1.0, 1.0,
        1.0, 0.0,
        0.0, 1.0,
        1.0, 0.0,
        0.0, 0.0,
        0.0, 1.0};
    
    glVertexAttribPointer(_position2, 3, GL_FLOAT, GL_FALSE,  sizeof(GLfloat) * 3, vertices);
    glVertexAttribPointer(_texture2, 2, GL_FLOAT, GL_FALSE,  sizeof(GLfloat) * 2, texturecoords);
    glDrawArrays(GL_TRIANGLES, 0, 6);

}

// - frameBuffe2->shaderCompiler3-> Render on screen 
-(void)render3{
    
    [self.shaderCompiler3 glUseProgram];
    [self activityFrameBuffer];
    glClearColor(0, 0, 1, 1);
    glClear(GL_COLOR_BUFFER_BIT);
    glViewport(0, 0, self.frame.size.width, self.frame.size.height);
    
    /*  The front is known self.frameBuffer2 The output texture unit of is  GL_TEXTURE1; glActiveTexture(GL_TEXTURE2);  and  glBindTexture(GL_TEXTURE_2D, [self.frameBuffer1 textureID]);  Yes, it will  self.frameBuffer2 The output texture unit of is from  GL_TEXTURE1  Change it to  GL_TEXTURE2; glUniform1i(_uni2, 2)  Yes, it will  GL_TEXTURE2  As  self.shaderCompiler3  Input texture of ;  The frame buffer texture output unit is rendered to the screen ; */
    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, [self.frameBuffer2 textureID]);
    glUniform1i(_uni3, 2);


    GLfloat vertices[] = {
    
        1.0, 1.0, 0.0,
        1.0, -1.0, 0.0,
        -1.0, 1.0, 0.0,
        
        1.0, -1.0, 0.0,
        -1.0, -1.0, 0.0,
        -1.0, 1.0, 0.0};
    
    GLfloat texturecoords[] ={
    
        1.0, 1.0,
        1.0, 0.0,
        0.0, 1.0,
        1.0, 0.0,
        0.0, 0.0,
        0.0, 1.0};
    

    glVertexAttribPointer(_position3, 3, GL_FLOAT, GL_FALSE,  sizeof(GLfloat) * 3, vertices);
    glVertexAttribPointer(_texture3, 2, GL_FLOAT, GL_FALSE,  sizeof(GLfloat) * 2, texturecoords);
    glDrawArrays(GL_TRIANGLES, 0, 6);

    [[QGEAGLContext sharedInstance] presentRenderbuffer];
}